Mi colour = "slate grey", Sn colour = "grey", SG colour = "brownish grey", YT colour = "grey-brown". It can be very difficult to distinguish between the greenish grey (1876) and grey (1889) versions of this stamp. The 1889 stamps vary from a slate grey colour to grey with a slight brownish tint. The 1876 stamps are slightly greenish. But sometimes the yellowing of the paper with age can make the 1889 stamps look a bit greenish. The 1876 stamps are about 5 times the price of the later 1889 stamps.
